Tiffen - 138MM ND 0.9 UNMOUNTED
Neutral Density filters reduce the amount of light passing through the camera lens without changing the color of the scene. Especially useful in bright light conditions to help prevent overexposure. Also allows proper exposure at a wider lens opening for reduced depth-offield to highlight a key subject by making the foreground and/or background out of focus.
Eliminates overly bright, washed-out images
Balances exposure
Controls depth-of-field
Allows slower shutter speeds to produce blurred motion effects.